Question

Question 1 Anti-cholinergic drugs (e.g. Cogentin) are effective in alleviating the symptoms of Parkinson's disease. Using a diagram, explain the mechanism of action of these drugs. Imagine a patient with Parkinson's and schizophrenia. Why would a typical anti-psychotic be less effective if co-administered with Cogentin? Question 2 Using two diagrams, one at initiation of treatment and one after6 weeks of treatment, expla in the mechanism of action SSRIS and the hypothesis for delayed therapeutic effect. What would happen if a patient being treated with an SSRI, after one week of treatment, went on vacation for two weeks and forgot her pills at home? Why?

Answer 1

PRE SYNAPTIC NEURON ACH ACH Bindiy to > MUSCARINIC RECEPTORS POST SYNAPTIC NEURON PRE SYNAPTIC Nev RoN ACHAcetylhalineelas P 3ynap nauro ACH ANTI CHOLINERGE MUSCARINIC RECEPTORS DRUGS ATROPINE BENZTROPINE POST SYNAPTIU DIPHENYDRAM INE NEURON TRIHEXYPHENIDYL

MECHANISM OF ACTION OF ANTICHOLINERGIC DRUGS

Anticholinergic drugs work by binding to muscarinic receptors thus inhibiting the neurotransmitter Acetylcholine( ACH) bind to muscarinic receptors and exert its action.

In parkinson's disease low levels of dopamine causes increase in acetylcholine and thus its binding to muscarinic receptors thereby increasing the nerve impulses causing muscles to contract eradically. So, anticholinergic drugs controls this excess nerve impulse transmission by binding to muscarinic receptor leaving no muscarinic receptor for acetylcholine to bind.

Other anticholinergic actions include bronchodilation, mydriasis, decreased G.I motility, decreased secretions of glands.

Examples include atropine,Scopalamine,Ipratropium,Tiotropium,dorifenacin,solifenacin, benztropine, dihenhydramine, trihexyphenidyl.

Typical antipsychotic drugs like haloperidol, loxapine, fluphenazine etc when coadministered with cogentin (Benztropine) then the therapeutic activity of typical antipsychotics( that is inhibiting the dopamine receptors) is decreased by centrally acting anticholinergics like cogentin. Also, it increases the risk of adverse effects such as C.N.S depression, tardive dyskinesia( involuntary movement disorder), confusion, hallucinations, heat intolerance etc.

It also causes excess anticholinergic effects when used together. Thus, worsening the symptoms of schizophrenia.